Observation of optical filtering effects with four-wave mixing in a cold atomic ensemble

TL;DR

This paper demonstrates optical filtering effects in four-wave mixing within cold atomic gases, showing how high-frequency components pass through unabsorbed while low-frequency parts are absorbed, and also demonstrates storage and retrieval of side peaks.

Contribution

It provides experimental evidence of optical filtering effects in FWM in cold atoms and introduces a method to store and retrieve specific optical components using Raman transitions.

Findings

High-frequency side peaks propagate without absorption.

Low-frequency components are absorbed by the atomic medium.

Backward side peaks can be stored and retrieved using Raman transition.

Abstract

We observe an optical filtering effect in four-wave mixing (FWM) process based on a cold atomic gas. The side peaks appear at the edges of pulse of generated optical field, and they propagate through the atomic media without absorption. The theoretical analysis shows that these side peaks corresponded to the high frequency part of pulse of generated signal, which means the atoms cannot response to the rapid change of the electromagnetic field in time. On the contrary, the low frequency components of generated signal are absorbed during the transmission through the atoms. In addition, we experimentally demonstrate that the backward side peak could be stored by using Raman transition in atomic ensemble and retrieved later.